Electronic Spectroscopies by a Novel STM with functional Semiconductor Tips

为了找到合适的STM针尖的半导体材料，本文采用STM/STS方法和带导电针尖的AEM方法研究了n-GaAs上InAs点自组装表面的近表面电学性质，并对n-GaAs上InAs点自组装表面的近表面电学性质进行了表征。在激光照射下的STS测量。结果，在InAs点结构附近检测到小的光响应信号，而从周围的润湿层区域检测到大的信号。此外，时间分辨的隧穿电流测量结果表明，这种光响应信号主要来自于光激发载流子引起的表面耗尽的减少。这些结果表明，表面耗尽被抑制附近的InAs点，这是非常类似的体InAs表面的电子积累。我们测量的静电力，这是工作之间的AFM针尖和样品，在类似的样品上，如上所述的AEM与导电针尖。通过在与外加交流偏置频率相同的两个频率和外加交流偏置频率的两倍频率上的锁相探测技术，我们成功地估计了表面的耗尽程度。此外，静电力数据表明InAs点附近的表面耗尽被抑制，这与STM/STS的结果一致，因此InAs覆盖GaAs是一种很有前途的半导体针尖材料，因为它的表面耗尽被抑制。

In order to find the proper semiconductor materials for STM tips, we have characterized the near surface electrical properties of self-assembled InAs dot-covered surfaces on n-GaAs through both the STM/STS measurements under the laser irradiation and the electrostatic force measurements by AEM with a conductive tip.We characterized the near surface electrical properties of The self-assembled InAs dot-covered surfaces on n-GaAs through the STM/STS measurements under the laser irradiation. As a result, the small photo-response signal was detected near the InAs dot structures, while the large signal was detected from the surrounding wetting layer region. In addition, the time-resolved tunneling current measurements revealed that such photo-response signal mainly came from the reduction of the surface depletion due to the photo-excited carries. These results indicates that the surface depletion is suppressed near the InAs dots, which is very similar as the bulk InAs surface where the electrons are accumulated.We measured the electrostatic force, which is working between the AFM tip and the sample, on the similar sample as above by the AEM with a conductive tip. Through the lock-in detection technique at the two frequencies which are the same and the double frequencies as applied AC bias frequency, we succeeded in estimating the degree of surface depletion. Moreover, the obtained electrostatic force data clearly indicated that the surface depletion is suppressed near the InAs dots, which is consistent with the STM/STS results.As a result, InAs covered-GaAs is one of the promising materials for the semiconductor tip because the surface depletion is suppressed on its surface.